The Ancient Greeks did not have a dedicated theory about the idea of sovereignty but they developed the conceptualisation of State and its implications so we in fact are able to at least have hints about their thoughts in regards also to sovereignty.
Plato sets up the basis from where the Greek philosophers and thinkers (even the modern ones) depart. Plato understands that we are in presence of a State “when we have got hold of enough people to satisfy our many varied needs, we have assembled quite a large number of partners and helpers together to live in one place […]”. He summarised with his conceptualisation all the elements we consider nowadays essential for the existence of a State: population, territory, government. Note that law is not mentioned but will be present throughout his work.
With The Republic “[…] there seems reason to believe it was monarchy which claimed [Plato’s] allegiance. A famous sentence of the Republic tells us, that there will be no rest from their troubles for the cities of Greece or for all mankind, until the days of philosopher kings; and from the Politicus we also learn the necessity of ideal and absolute monarchy. […] Reason, being one and indivisible, rules the spirit and the multitude of desires in the individual mind: reason, incarnate in one sovereign, must rule all other classes in the State. In such a sovereign the theories of the Republic culminate. […]The Platonic theory of monarchy is expounded in the Politicus”. However interesting, this point is not relevant here. Plato revaluates several forms of governments from different angles. It is true he considers monarchy as the best option in theory but he knows—being a pragmatic—that democracy results more feasible. The key detail for here: the sovereignty of a State remains a “human” attribute.
Let us turn the attention to what Plato says in the Politicus in relation to the Guardians, representatives, statesman or government:
“[…] we started by taking theoretical knowledge and distinguishing an instructional part of if, and we then drew on an analogy to make up the term ‘producer-instructional’ for a further subdivision. Next, within this ‘producer-instructional’ branch we isolated the not unimportant art of maintaining creatures. We found that a category of creature-maintenance was herd-maintenance, and that a category of herd-maintenance in its turn was the herding of creatures with feet. Within the herding of creatures with feet, the crucial segment we distinguished was the art of maintaining those which lack horns. And if you want to encapsulate in a single term the relevant subdivision of this art of maintaining creatures which lack horns, you have to combine at least three components and call it the branch of knowledge which is concerned with ‘the herding of species which cannot interbreed’. As for subdividing this class, since the art of herding human beings is the only section left which deals with two-footed gregarious creatures, then it is exactly what we are after – the art we’ve been calling both kingship and statesmanship”.
Indeed, it seems Plato introduces a simple classification. But after more careful consideration we may see that he presents the elements that integrated—and still do —the theory of a ruler and the State: gregarious two-footed creatures (we would add, with consciousness) that are used to being in groups. He assumes they will have needs and in order to better cover their needs they will need direction; hence, the reciprocal relation represented-representative—i.e. sovereignty and its reflection. For the ones into political sciences and political theory, a very early reference to Nozick and his “aggregations.”
Another key development evident in Plato’s work: having different options in terms of forms of government, it is only one that truly reflects the idea of public sovereignty: “[…] ‘dictatorship’ is the term for the management by constraint of unwilling subjects, whereas ‘statesmanship’ is the term for the management by consent of willing, two-footed, gregarious creatures. So [the one] […] with this particular kind of managerial expertise is a true statesman-king […]”.
As it has previously been mentioned in this post, it is clear Plato’s preference for monarchy but being a practical thinker and having experienced many realities throughout his life he concedes that “[…] in other cities there had been a development which had almost everywhere followed the same order, from monarchy to aristocracy, from aristocracy to tyranny, from tyranny to democracy”.
For that reason it is at least hard to agree with Barker when he concludes that “[t]he statesman has an infinite complexity of circumstances, an infinite variety of characters, to handle; and like a physician, he must be left untrammelled by any book of laws, if he is to handle them as he should. The variability of his matter demands a corresponding flexibility in his power. States which bind their rulers to act according to law lose that flexibility. [...] The ideal of Plato would thus appear to be the absolute monarch of a subject people, unfettered by public opinion and unhampered by law”. From The Republic to the Politicus and the Laws a common thread may be identified: sovereignty as an attribute of the people that are the polis.
The idea of the representative evolves as his works and mostly his experience do so. Although he is inclined at first for a monarch ruling with absolute power he later on understands the idea of democracy as a better and more practical solution. It is important to highlight once again: sovereignty remains in all his works within the society. That society because of its needs requires representation. The representatives (or Guardians) are a reflection of the people’s will. Having one person representing them or a group does not change the essence of his idea.
Next time Plato’s Statesman.
 Plato, The Republic, translated by D. Lee, Penguin Books, 1987, p. 58.
 Barker, Ernest, The political thought of Plato and Aristotle, Dover Publications Inc., 1959, pp. 164/165.
 Plato, Statesman, translated by R. Waterfield, Cambridge texts in the History of political thought, 1995, pp. 18/19.
 Plato, Statesman, translated by R. Waterfield, Cambridge texts in the History of political thought, 1995, p. 32.
 Barker, Ernest, Greek political theory: Plato and his predecessors, Methuen & Co., Ltd., 1951, p. 3.
 Barker, Ernest, The political thought of Plato and Aristotle, Dover Publications Inc., 1959, p. 167/168.